The present invention relates to a double-seat valve having two valve discs which move independently of and relative to one another.
Double-seat valves with independently movable valve discs are known in the art, in which after a predetermined stroke to an open position, one of the valve disc lies against the other valve disc and together with the latter forms a hollow chamber from which a draining conduit leads outside of the valve. Double-seat valves are utilized in beverages industry. When the valve discs are in the above-mentioned open position, the hollow chamber communicates with the draining conduit which has an outlet portion spaced from the valve seat and leading outside. In such a construction leakage of a valve can be fast detected due to outwardly flowing leakage liquid and can be eliminated before further damages occur.
With growing automation, a limit switch between the valve discs is provided for detecting respective positions of the valve discs, and the thus-obtained impulses are transmitted to a light screen which represents in a simple manner the respective closed and open positions of complete valve batteries. In this connection, the valves can operate with a guaranteed stroke. This means that a prestroke of the first valve disc which is moved by a control device, automatically drives the second valve disc, with interposition of an intermediate spring in some cases. Such a valve is disclosed, for example, in the German Pat. Nos. 855,183 and 2,632,587. These valves have, however, the disadvantage in that the second valve discs must be movably guided relative to the first valve disc on its own valve shaft in axial direction. Thereby, a complicated sealing is required, on the one hand, and a split cross-section takes place which is very disadvantageous, especially on hygienic grounds, in the beverages industry and is, therefore, undesirable. Moreover, pressure springs must be utilized for bridging of the intermediate strokes. Such valves have considerable total height which is disadvantageous when the valves are arranged in tank batteries wherein at least several valves must be located laterally adjacent to one another or one above the other. A further disadvantage is connected with fatigue of the pressure springs which occurs in these valves. After a certain period of use, leakage resulting from the insufficiently closed valve takes place, before it is visibly broken.